The present invention relates to the use of certain lectins for the control of insect pests.
Lectins are a heterogeneous class of (glyco) proteins grouped together based upon their ability to recognize and bind carbohydrate moieties of glycoconjugates. Chitin, the principal structural carbohydrate of insects, is a polymer of N-acetyl glucosamine [GluNAc] and various lectins with sugar binding specificities for GluNAc have been disclosed with insecticidal activity against certain agricultural pests.
EP-A-0351924 (Shell Internationale Research Maatschappij B.V.) relates to a transgenic plant comprising a lectin gene expressing a lectin within the plant foreign to the plant as found in nature. In particular, it discloses that pea lectin has been inserted into tobacco, and the transgenic plant has some degree of insect resistance.
EP-A-0427529 (Pioneer Hi-Bred International, Inc) discloses that selected plant lectins have been found to be larvicidal against a number of common insect pests or agricultural crops.
Many lectins are known to be toxic to mammals and birds. For example, the lectins of Phaseolus vulgaris are poorly digested by rats and thus are able to react with intestinal cells causing disruption of the brush borders of duodenal and jejunal enterocytes. As a result, abnormal absorption of potentially harmful substances occurs, leading to severe toxic effects (Pusztai et al, 1979).
There is a need, therefore, to identify lectins which are toxic to insects but at the same time do not exhibit toxicity to mammals or birds. These would be useful in crop protection applications without restriction on the food use of the material in which the foreign lectin is to be presented.